The present disclosure relates to image processing apparatuses, image processing methods, and programs and, more specifically, to an image processing apparatus, an image processing method, and a program that produce the effect of depth control without degrading the image quality.
For people to perceive the three-dimensional (3D) form and the depth of an object, information for use includes binocular stereo information with two eyes and monocular stereo information with one eye. People use both the binocular and monocular stereo information to perceive the 3D form and the depth of an object and of a space. The binocular stereo information includes binocular parallax, horizontal convergence, and others, and the monocular stereo information includes shading, contrast, color, spatial frequency, shielding status, and others.
For enhancing the 3D form and the depth of an object in an image displayed on a two-dimensional (2D) display to let a viewer perceive that the image is 3D, the image may be displayed with a larger binocular parallax being the binocular stereo information, for example.
However, displaying the object image with a larger binocular parallax causes problems as below considering the human eyeball structure and the visual performance. That is, the human eyeballs are normally converged inwardly rather than being parallel. Therefore, when the binocular parallax becomes larger than the pupil distance, this causes the eyeballs to diverge outward. The pupil distance varies depending on the age and sex of viewers, and as to viewers whose pupil distance is narrower than others, their eyeballs are easily diverged.
Therefore, displaying an image with a larger binocular parallax to enhance the 3D form and the depth of an object therein may easily cause eye strain.
In consideration thereof, proposed is to use the monocular stereo information to enhance the 3D form and the depth of an object. As an example, Japanese Patent Application Laid-Open No. 2001-238231 proposes to enhance the depth of an object by changing how the object looks depending on the depth position of the object in an image, e.g., changing shading, shielding status, and a degree of blurring.
In Japanese Patent Application Laid-Open No. 2001-238231, however, there is no specific description about how to set which parameter value based on which calculation equation. Parameter value setting with trial and error offers no guarantee that the resulting right- and left-eye images look natural for viewers and cause them no eye strain, or rather the images may not look natural for the viewers and cause them discomfort or eye strain.
In order to solve such problems, the applicant of the present application proposes technologies of quantifying the relationship between the monocular stereo information and the depth perception, and controlling the 3D form and the depth of an object using the quantitative relationship (Japanese Patent Application Laid-Open Nos. 2011-113363 and 2012-247891). Japanese Patent Application Laid-Open No. 2011-113363 specifically describes the technology of quantifying the relationship between the contrast and the depth perception, and controlling the 3D form and the depth of an object by contrast adjustment using the quantitative relationship. Japanese Patent Application Laid-Open No. 2012-247891 specifically describes the technology of quantifying the relationship between the contrast/spatial frequency and the depth perception, and controlling the depth of an object by contrast adjustment on a spatial frequency basis using the quantitative relationship.